Exploring the diversity and metabolic potential of actinomycetes from temperate marine sediments from Newfoundland, Canada.

Marine sediments from Newfoundland, Canada were explored for biotechnologically promising Actinobacteria using culture-independent and culture-dependent approaches. Culture-independent pyrosequencing analyses uncovered significant actinobacterial diversity (H'-2.45 to 3.76), although the taxonomic diversity of biotechnologically important actinomycetes could not be fully elucidated due to limited sampling depth. Assessment of culturable actinomycete diversity resulted in the isolation of 360 actinomycetes representing 59 operational taxonomic units, the majority of which (94 %) were Streptomyces. The biotechnological potential of actinomycetes from NL sediments was assessed by bioactivity and metabolomics-based screening of 32 representative isolates. Bioactivity was exhibited by 41 % of isolates, while 11 % exhibited unique chemical signatures in metabolomics screening. Chemical analysis of two isolates resulted in the isolation of the cytotoxic metabolite 1-isopentadecanoyl-3ß-D-glucopyranosyl-X-glycerol from Actinoalloteichus sp. 2L868 and sungsanpin from Streptomyces sp. 8LB7. These results demonstrate the potential for the discovery of novel bioactive metabolites from actinomycetes isolated from Atlantic Canadian marine sediments.

Multilevel modeling of fetal and placental growth using echo-planar magnetic resonance imaging.

OBJECTIVE: To quantify longitudinal increases in fetal, fetal liver, and fetal brain volume using echo-planar magnetic resonance imaging and to quantify the results using appropriate statistical modeling. METHODS: Fifty-six singleton fetuses were studied using echo-planar (snap-shot) magnetic resonance imaging, between 19 weeks and term. They were assessed at a variety of different gestations and on a different number of occasions, thereby requiring multilevel statistical modeling to analyze the pattern of fetal growth. RESULTS: Fetal volume varied according to the following equation: square root (radical) [fetal volume]=-37.71+2.17 x gestational age (GA)-0.004 x GA(2). The equation for fetal liver volume was radical[fetal liver volume]=9.47+0.56 x GA-0.02 x GA(2), for fetal brain volume was radical[fetal brain volume]=15.50+0.69 x GA-0.014 x GA(2), and for placental volume radical[placental volume]=28.54+0.95 x GA-0.039 x GA(2), where GA is the gestational age in weeks -30. CONCLUSION: The assessment of fetal, fetal organ, and placental volume was feasible using echo-planar magnetic resonance imaging from 20 weeks to term. Multilevel statistical modeling can be applied to analyze sets of data with different measurements on different occasions. This information is useful clinically to assess abnormal fetal growth.

Fetal and placental volumetric and functional analysis using echo-planar imaging.

Recent and past work using echo-planar imaging (EPI) in pregnancy has allowed important anatomic and physiological information to be obtained, giving advantages over conventional radiological methods such as ultrasound. EPI is a quick, convenient method of measuring organ volumes. The volumetric estimates throughout gestation correlate well with known fetal weight at these gestations. Relaxation time measurements also can be made in the placenta and lungs. By combining the changes in relaxation and volume with gestation in the future, it may be possible to develop an "index of maturity." This could be used to accurately reflect lung maturation. T1 and T2 parameters in the placenta decreased with gestational age and with abnormal placentation. EPI can be used to assess perfusion in the placenta and flow in the uterine arteries because of its rapid acquisition times. These techniques have been applied to assess perfusion within the fetal brain.

Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome.

OBJECTIVE: We sought to identify clinical factors at diagnosis that predict outcome in twin-twin transfusion syndrome. STUDY DESIGN: In this retrospective series 23 patients with twin-twin transfusion syndrome were seen in a tertiary referral fetal medicine center over a 3-year period. Ten antenatal factors were assessed to determine their ability to predict outcome by use of ordered logistic regression. These factors were the following: (1) absent or reversed end-diastolic flow in the umbilical artery, nonvisible bladder, anhydramnios, and estimated fetal weight of <3rd percentile in the donor; (2) pulsatile umbilical vein, either absent or reversed end-diastolic flow in the ductus venosus, or both, and tricuspid-mitral valve regurgitation in the recipient; and (3) gestational age at presentation, estimated fetal weight discordancy, absent arterioarterial anastomosis, and spontaneous rupture of the membranes or cervical change as pregnancy factors. Management comprised serial amnioreduction (n = 10), selective feticide (n = 5; 4 also had amnioreduction), septostomy (n = 4; 1 also had amnioreduction), and delivery (n = 2). Two patients miscarried before treatment. RESULTS: The chance of survival of both twins fell and double deaths increased linearly with increasing number of adverse factors (P =.026). A low chance of survival was independently associated with absent or reversed end-diastolic flow in the donor umbilical artery (P =.02) and with a pulsatile umbilical vein or absent or reversed end-diastolic flow in the ductus venosus (P =.03) of the recipient. The probability of at least one twin surviving was only 33% if there was absent or reversed end-diastolic flow in the donor umbilical artery or 37% when abnormal venous recordings were seen in the recipient. An arterioarterial anastomosis detected at diagnosis also influenced prognosis, with all twins surviving when an arterioarterial anastomosis was identified (P =.04). CONCLUSIONS: Three factors identified at diagnosis independently predict poor survival in twin-twin transfusion syndrome-absent or reversed end-diastolic flow in the donor umbilical artery, abnormal pulsatility of the venous system in the recipient, and absence of an arterioarterial anastomosis. These may have a role in the counseling of parents and in selecting the appropriate treatment strategy.

In utero perfusing fraction maps in normal and growth restricted pregnancy measured using IVIM echo-planar MRI.

The aim of this study was to measure and portray blood movement in the placenta in vivo in normal and growth restricted pregnancies, using Intra Voxel Incoherent Motion (IVIM) magnetic resonance imaging. Thirteen patients with apparently normal healthy pregnancies were scanned at 31+/-7 (mean+/-s.d.) weeks gestation and seven patients with intrauterine growth restriction (IUGR) were scanned at 31+/-4 weeks. A region of interest (ROI) was defined encompassing the placenta between the decidual and chorionic plates. The volume of moving blood within each imaging voxel of the ROI was then calculated as a percentage of the total voxel volume (f per cent). This information was colour coded to produce maps of moving blood volume. The placenta was segmented length ways into two zones of approximately equal area, termed inner and outer, the latter being adjacent to the uterine wall. f was fitted for the average in the outer zone (f(out)) and inner zone (f(in)). The parameter (f(out)-f(in)) was then calculated for each subject. This was positive in 12/13 of the normal cases and zero for one case (+10 per cent+10, mean+/-s.d.). For pregnancy affected by IUGR this value was negative in all cases (-4 per cent+/-3). Perfusion fraction mapping identified differences in function within the normal placenta in vivo, and between the placentae of normal and IUGR pregnancies. The technique has potential applications in managing, and investigating the aetiology of, pregnancy compromise.

Infants exposed to MRI in utero have a normal paediatric assessment at 9 months of age.

Any differences in detailed paediatric assessment at 9 months of age in infants exposed to echo planar MRI in utero from 20 weeks gestation to term were investigated by performing a case controlled prospective observational study of 20 infants. They had all had serial echo planar MRI in the antenatal period and were compared with a control group born at the same time who had not. Statistical analysis employed likelihood ratios, odds ratios and 95% confidence intervals. The mothers of the control infants had a significantly higher standard of educational attainment (p = 0.005). A small but significant decrease in length (p = 0.047), and an increase in gross motor function (p = 0.023) of the fetuses exposed to echo planar imaging were demonstrated. No other significant developmental or social differences were seen between the two groups. Infants at 9 months of age did not demonstrate any gross abnormality likely to be related to exposure to echo planar MRI in utero.

In vivo intravoxel incoherent motion measurements in the human placenta using echo-planar imaging at 0.5 T.

This paper presents the first in vivo measurements of intravoxel incoherent motion in the human placenta, obtained using the pulsed gradient spin echo (PGSE) sequence. The aims of this study were two-fold. The first was to provide an initial estimate of the values of the IVIM parameters in this organ, which are currently unknown. The second aim was then to use these results to optimize the sequence timings for future studies. The moving blood fraction (f), diffusion coefficient (D), and pseudo-diffusion coefficient (D*) were measured. The average value of f was 26 +/- 6 % (mean +/- SD), D was 1.7 +/- 0.5 x 10(-3) mm2/sec, and D* was 57 +/- 41 x 10(-3) mm2/sec. For the optimized values of b, the expected percentage uncertainty in the fitted values of f, D, and D* for the placenta were sigmaf/f = 14.9%, sigmaD/D = 14.3%, sigmaD*/D* = 44.9%, for an image signal-to-noise of 20:1, and a total imaging time of 800 sec.

High failure rate of umbilical vessel occlusion by ultrasound-guided injection of absolute alcohol or enbucrilate gel.

The success rate for injected umbilical vascular occlusion in the published literature exceeds 85 per cent. In this study we assessed the efficacy of two forms of injected sclerosants in achieving umbilical vessel occlusion. 12 cases of attempted ultrasound-guided occlusion over a 2 1/2 year period were reviewed. These were monochorionic (MC) twins (n=6), dichorionic twins (n=3) and singletons (n=3) undergoing fetocide for severe anomalies, or impending fetal demise. Absolute alcohol (n=6), enbucrilate gel (n=5) or both (n=1) were used in an attempt to achieve vascular occlusion. Complete vessel occlusion was achieved in only a third of cases (4/12), three with absolute alcohol and one with enbucrilate gel. In MC twins occlusion was successful in two of six cases. In contrast to previously published data, this large series, containing more cases than the total previously reported, shows considerably poorer success rates for injected umbilical vascular occlusion. Injection of currently available sclerosants can no longer be recommended for umbilical vascular occlusion in human fetuses.

The changes in magnetic resonance properties of the fetal lungs: a first result and a potential tool for the non-invasive in utero demonstration of fetal lung maturation.

OBJECTIVE: To measure magnetic resonance parameters T1 and T2 of the fetal lungs and investigate the relationship of these parameters to changes in volume and gestation. DESIGN: Prospective cross-sectional study. SETTING: Large teaching hospital in Nottingham and the Magnetic Resonance Centre at the University of Nottingham. POPULATION: Normal pregnancies from 20 weeks to term. METHODS: T1, T2, and lung volume were measured in the fetus using echo-planar magnetic resonance imaging. MAIN OUTCOME MEASURES: The relationship of T1 and T2 to gestational age and lung volume. RESULTS: Linear regression demonstrated a significant relationship (P < 0.001) between gestational age and lung volume, T1 and T2. There was also a significant relationship between lung volume and T1 and T2 (P < 0-001). CONCLUSIONS: Relaxation time measurements give additional information to lung volume estimation in the assessment of lung physiology in utero. We have demonstrated the progressive changes which take place in the fetal lungs between 20 weeks and term. The physiological changes which can be demonstrated with this non-invasive technique may have an important application in the demonstration of fetal lung maturity in a prospective non-invasive manner.

First-trimester cord entanglement in monoamniotic twins.

OBJECTIVE: Monoamniotic twinning occurs in only 1% of twin pregnancies, but carries a high perinatal mortality rate. Early and reliable diagnosis is essential if attempts are to be made to reduce the complication rate. We report color Doppler demonstration of cord entanglement in the first trimester, which is diagnostic of monoamnionicity. METHODS: Two patients with twin pregnancies were examined in the first trimester with pulsed and color Doppler insonation of their umbilical arteries. RESULTS: Cord entanglement was suspected and proved by demonstrating differing fetal heart rate patterns in the same direction on umbilical artery Doppler analysis of a common mass of cord vessels. Following appropriate counselling, medical amnioreduction was induced at 20 weeks of gestation to reduce fetal movements and worsening cord entanglement. Delivery was by elective Cesarean section at 32 weeks' gestation and monoamnionicity was confirmed. CONCLUSION: We report a new sign for the demonstration of monoamnionicity in twin pregnancies in the first trimester. This should improve the reliability of early diagnosis, but further studies are required to confirm that, if cord entanglement occurs, it is usually present by the end of the first trimester.

Assessment of fetal lung growth in utero with echo-planar MR imaging.

PURPOSE: To measure changes in normal fetal lung volume with increasing gestation by using echo-planar magnetic resonance (MR) imaging. MATERIALS AND METHODS: Fifty-six singleton fetuses were examined longitudinally with respect to lung volume by using echo-planar MR imaging between 19 weeks gestation and term. RESULTS: Lung volume increased exponentially with gestation from 8 to 125 mL. Volume was related to gestation by using the equation, volume = 0.8375e0.1249g (R2 = 0.77), where g = gestation. Lung volume had a direct relationship to fetal volume with increasing gestation (R2 = 0.75). There was no significant relationship between amniotic fluid volume and lung volume (R2 = 0.11). CONCLUSION: Variation in lung volumes can be assessed by using echo-planar MR imaging, regardless of variations in amniotic fluid volume. These measurements are less than those obtained from postmortem and neonatal studies but are similar to those obtained by using three-dimensional ultrasonography. Lung volume estimations obtained by using echo-planar imaging may have important clinical and research applications when noninvassive assessment of lung volume is required.

The investigation of placental relaxation and estimation of placental perfusion using echo-planar magnetic resonance imaging.

Echo-planar imaging (EPI) is a form of magnetic resonance imaging (MRI) which acquires images in milliseconds rather than minutes as with conventional MRI. The images produced using EPI are affected by the physiological environment in which the hydrogen atoms producing the signals are found, a process referred to as relaxation. Also by producing images a matter of milliseconds apart, quantification of perfusion within the tissue being imaged is feasible. The objective of this study was to investigate T1 and T2 relaxation times along with perfusion in placentae from normal pregnancies at different gestations and also to compare these to pregnancies complicated by abnormal placental function. A cross-sectional study of normal and compromised pregnancies from 20 weeks to term and a longitudinal study of normal pregnancy were performed. Placental T1, T2 relaxation times, and perfusion were measured using echo-planar magnetic resonance imaging. Placental T1 and T2 relaxation times decreased in normal pregnancy (P<0.001). Relaxation times in pregnancies associated with placental pathology appeared to be reduced for that gestation although the numbers were too small to allow any statistical validation. No differences in placental perfusion with gestation or between normal and compromised pregnancy were demonstrated using this technique. This is the first demonstration of placental magnetic resonance relaxation and perfusion measurements in normal pregnancy using echo-planar magnetic resonance imaging. In the future it may be possible to identify compromised pregnancies by differences in placental T1 and T2 relaxation times, using this novel non-invasive technique.

In vivo perfusion measurements in the human placenta using echo planar imaging at 0.5 T.

This paper presents the first in vivo measurements of perfusion in the human placenta from 20 weeks gestational age until term, using the non-selective/selective inversion recovery echo-planar imaging sequence, in which data is alternately acquired following a selective and non-selective inversion pulse. Twenty pairs of images were collected, two each at the following inversion times: 20, 310, 610, 910, 1110, 1410, 1910, 2810, 3310, and 4510 ms with the sequence being repeated with a repetition time (TR) of 10 s. The results of these measurements were used to suggest the optimum sequence for future work in terms of the signal to noise ratio in the measured perfusion rate in a given measurement time. The sequence was also analyzed to determine the expected variability in the measurements. In normal pregnancies the average value of perfusion rate was found to be 176 (standard error = +/-24) ml/100 mg/min. (n = 16, standard deviation = 96 ml/100 mg/min). The expected variability in the measured parameters due to signal to noise ratio considerations alone was calculated to be 71%. For a maximum scanning time of 400 s, the optimum sequence for measuring placental perfusion was found to require 8 repetitions at each of 10 inversion times which were geometrically spaced (given by a(o), a(o)r, a(o)r2, a(o)r3, . . .), with a(o) = 850 ms, r = 1.073 and TR = 5 s, giving a pixel variability of 38%. Other timing schemes are recommended for measuring perfusion in other anatomical regions with different values of perfusion rate and longitudinal relaxation time.

Failure to detect intrauterine growth restriction following in utero exposure to MRI.

Echo planar imaging is a form of MRI with short image acquisition times, which permits in utero fetal imaging without motion artefacts. Echo planar imaging has been used to measure accurately fetal organ volume and to assess placental function. Two small animal studies have suggested the possibility of intrauterine growth restriction consequent upon MRI. We thus performed a prospective study of pregnancies in which fetuses were exposed to echo planar imaging, compared with a control group in which there was no in utero echo planar imaging exposure. There were no significant differences between the groups when maternal age, parity, proportion of smokers and proportion of Caucasian women were compared. Although the gestational age of delivery was lower in the echo planar imaging group, the proportion of women delivering prematurely was not significantly different. Although infant birthweights were significantly lower in the MRI group, the corrected birthweight for gestational age centiles (individualized birthweight ratio) was not significantly different between the two groups. In utero exposure to echo planar imaging thus did not have a marked effect on intrauterine fetal growth. A 10 year follow-up study of all infants imaged in utero is being performed.

In vivo relaxation time measurements in the human placenta using echo planar imaging at 0.5 T.

This paper presents the first in vivo measurements of the nuclear magnetic resonance relaxation times T1 and T2 at 0.5 T in the human placenta from 20 weeks gestational age until term, in both normal and compromised pregnancies. T1 measurements were performed by using both an inversion recovery sequence and the Look-Locher echo planar imaging (EPI) sequence on a total of 41 women with normal pregnancies and 11 women with compromised pregnancies. T2 measurements were performed by using a spin-echo EPI sequence on 36 women with normal pregnancies and 14 women with compromised pregnancies. In normal pregnancies, both the T1 values measured with the inversion recovery sequence and the T2 values were found to decrease with gestational age, the linear regression results gave T1 = -9.1t + 1538 r2 = 0.23 p = 0.03. T2 = -4.0t + 338 r2=0.47 p =410(-6) where t is the gestational age in weeks, and T1 and T2 are the relaxation times in milliseconds. T1 values measured very rapidly with the Look-Locher EPI sequence, but, therefore, with a much lower signal-to-noise ratio, showed no significant trends. The T1 values measured in the abnormal group were significantly lower than those measured in the normal group. Four out of eight patients with compromised pregnancies had placental T1 values lying outside the 90% confidence limits for the normal population based about the regression line, significantly more than expected by chance (p = 0.005). Ten out of fourteen of the T2 measurements in the abnormal group were below the regression line established for the normal group, with 4 lying below the 90% confidence interval, although these trends were only just significant (p = 0.06 and p = 0.03).

Non-invasive mapping of placental perfusion.

BACKGROUND: We aim to develop a clinical technique for the non-invasive measurement of placental perfusion, to enable early detection of intrauterine growth restriction (IUGR). Pregnancies with this complication are characterised by low placental perfusion. METHODS: We measured placental perfusion by means of perfusion-sensitive echoplanar imaging (EPI); a rapid method of making magnetic resonance images. Perfusion measurements were done on six healthy volunteers with normal pregnancies and nine with pregnancies complicated by IUGR. Perfusion maps were created to assess the relation between placental perfusion and fetal size at birth. FINDINGS: Pregnancies complicated by IUGR differed significantly from normal pregnancies in patterns of perfusion within the placenta (p<0.0001, ANOVA). Subsequent analysis showed that the proportion of placentas with low perfusion rates was higher in the IUGR group than in the normal group. A significant correlation between areas of reduced placental perfusion and fetal size was demonstrated (p=0.041, Spearman's rank correlation). INTERPRETATION: Non-invasive imaging of placental perfusion by means of EPI has potential as a clinical tool in assessing the dynamics of placental perfusion.

Demonstration of changes in fetal liver erythropoiesis using echo-planar magnetic resonance imaging.

This study investigated the variation in magnetic resonance characteristics of the fetal liver during a time of changing erythropoietic function. Echo-planar imaging was carried out in 25 normal pregnant women at 20 and 26 wk gestation. The signal intensity from regions of the fetal liver, background image, and maternal back muscle and the highest signal intensity from the maternal spinal cord were measured and compared with the signal intensity of amniotic fluid. Data are expressed as ratios, in arbitrary units (median pixel values; interquartile range shown in parentheses), and analyzed with the use of Wilcoxon's signed-rank test. At 20 wk, the signal intensity ratio of liver to amniotic fluid was 0.309 (0.231-0.365). At 26 wk, the ratio was 0.544 (0.429-0.616). The change was highly significant (P < 0.0001). No change in the signal intensity ratios of amniotic fluid compared with other measured parameters was noted. These data are consistent with known changes in fetal liver erythropoiesis occurring between 20 and 26 wk gestation and have potential use in early noninvasive physiological assessment of the fetus.

The aetiology and management of twin-twin transfusion syndrome.

Twin-to-twin transfusion syndrome presents in the mid-trimester with gross discordance in amniotic fluid volume, and complicates 10-15 per cent of monochorionic twins. Recent studies suggest a primary vascular basis in which a paucity of the bidirectional superficial anastomoses normally found in monochorionic twins is unable to compensate for haemodynamic imbalance resulting from unidirectional transfusion along deeper arterio-venous anastomoses. It is associated with high rates of perinatal mortality from ruptured membranes, hydrops and growth restriction, and a significant morbidity from cardiac and neurological sequelae in particular. Serial aggressive amnioreduction is the current treatment of choice, with survival in around two thirds of cases. In the remaining third, with features suggesting a poor outcome, selective fetocide may have a role. Current attempts at vascular ablative therapies have been associated with inferior survival rates, but the long term therapeutic goal remains the identification and ablation of the shared chorionic vasculature.

The development of magnetic resonance imaging in obstetrics.

Following recent developments in imaging techniques which overcome the problem of fetal motion, magnetic resonance imaging (MRI) has the potential to improve non-invasive fetomaternal assessment. This article catalogues the development of MRI and the potential that exists for its use in obstetrics in the future.